Stable checkpoint — Order/Product/OrderLine foundation + common SHA aligned

Includes :
- Product entity (V7 migration + JPA + minimal CRUD)
- Order entity (V8 migration + JPA + minimal CRUD)
- OrderLine entity (V9 migration + nested controller)
- Common submodule bumped to 3e7acba (bump-common-everywhere.sh + ADR-0055)

Post-merge main pipeline #2480584002 green at 15:52.